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Abstract:
CO2 methanation, also known as the Sabatier reaction, is of great environmental interest as a sustainable process for energy production and storage. Herein, we report the development of a NiLa2O3 catalyst for CO2 methanation prepared upon reduction of a LaNiO3 perovskite precursor. The perovskite-based catalyst exhibits enhanced activity, high methane selectivity and improved stability when compared to Ni–La2O3 prepared through conventional impregnation methods. The transformation of the LaNiO3 perovskite precursor upon thermal activation in H2 was found to have a profound impact on the catalytic properties of the resulting material. The size and stability of exsolved Ni nanoparticles after prolonged reaction were investigated using ex situ electron microscopy. Synchrotron-based X-ray absorption fine structure (XAFS) spectroscopy, as well as soft and tender X-ray photoelectron spectroscopies (AP-XPS/HAXPES), provides detailed insights into the evolution of bulk and surface phases during the transition of the perovskite to its active catalytic state. Our findings indicate that processes beyond the well-established exsolution of nanoparticles, such as lanthana spillover onto nickel, may occur during H2 activation. More importantly, in situ spectroscopy under CO2 methanation conditions revealed that the surface's affinity for La-hydroxide or La-carbonate formation significantly influences the reactivity. Specifically, we found that La-hydroxide acts as a precursor for the formation of La-oxycarbonate (hexagonal La2O2CO3 phase), a crucial element of the active exsolved catalyst. In contrast, in the absence of La-hydroxide, La-carbonates (La2(CO3)3) formed on the surface, blocking the active sites of the supported catalyst. Our research examines hitherto unrecognized processes affecting the reactivity of exsolved perovskites, highlighting LaNiO3 as a promising catalyst for CO2 methanation.
